In recent years, a non-contact IC card and an IC tag in which transmitting and receiving of an electromagnetic signal output by a reader/writer are performed without contact have been developed and put to practical use. A planar antenna which constitutes an antenna circuit pattern (a circuit pattern) of such non-contact IC card or IC tag includes A) a planar antenna in which the circuit pattern is formed by etching a copper foil, an aluminum foil or the like pasted together with a plastic film (for example, Patent Document 1), B) a planar antenna in which the circuit pattern is formed by printing a conductive coating material in a predetermined form on a plastic film or a plastic sheet (for example, Patent Document 2), C) a planar antenna in which the circuit pattern is metal-plated after it is formed by printing a conductive coating material in a predetermined form on a plastic film or a plastic sheet (for example, Patent Document 3), and D) a planar antenna in which the circuit pattern is formed by drawing-out with a drawing blade an antenna circuit pattern from a plastic film in which copper foils or aluminum foils are layered (for example, Patent Document 4).
However, in the case of the above-described A), there is a necessity of removing an unnecessary part with etching after the circuit pattern is formed on the copper foil, the aluminum foil, or the like pasted together with the plastic film with a photo resistor the like. Especially, it is difficult to lower costs because the whole or a part of the resist layer where the circuit pattern is formed has to be removed in order to electrically connect the terminal parts of an electronic component and an antenna. Further, for planar antennas in which the circuit pattern is formed by printing the conductive coating material as in the above-described B) and C), the electric resistance is easy to become high. Although the coating thickness can be increased in order to decrease the resistance, if so, the circuit pattern cracks when it is bent and the communication property of the antenna is easy to be unstable. Furthermore, for a planar antenna in which the circuit pattern is formed by metal-plating after printing with a conductive coating material as in the above-described C), adhesiveness of the metal-plated layer deteriorates at a part with a fine line width, the circuit pattern is easy to slip off in a transporting step, and high costs at a metal-plating step cannot be avoided. Then, in the case of the above-described D), there is a problem that it is difficult to improve the line width accuracy of the circuit pattern.
On the other hand, regarding an electric connection of the circuit pattern and an electronic component such as an IC chip, a non-contact IC card and an IC tag are proposed in which an anisotropic conductive adhesive layer or a metal wire is provided at a connection terminal part of the circuit pattern and an electronic component such as an IC chip is directly placed thereon (for example, Patent Documents 5 to 8).
However, because inexpensive aluminum is often used as a conductor constituting the circuit pattern, and in that case, an oxide layer is easily formed on the surface of aluminum, there is a problem that adhesiveness of anisotropic conductive adhesive and aluminum decreases and the electric resistance value is easy to increase even though the electronic component is connected to the connection terminal part of the circuit through the anisotropic conductive adhesive. Especially, the planar antenna may be subjected to a severe acceleration test in which it is kept under a high temperature and high humidity of 40° C. and 90% RH for 2 weeks with the assumption of the environment where an IC tag is used in order to confirm whether there is deterioration of the performance as a planar antenna or not. However, by performing this test, the oxide layer on the surface of aluminum increases further, the connection resistance becomes large, and sometimes there is a problem that communication with a reader/writer easily becomes unstable.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2003-37348 (Claims)    Patent Document 2: JP-A No. 2004-180217 (Claims)    Patent Document 3: JP-A No. 2004-529499 (Claims)    Patent Document 4: JP-A No. 2003-37427 (Claims)    Patent Document 5: JP-A No. 08-310172 (Claims)    Patent Document 6: Japanese Patent No. 2818392 (Claims)    Patent Document 7: JP-A No. 2000-113144 (Claims)    Patent Document 8: JP-A No. 2002-42098 (Claims)